macbre

This extension has been inspired by http://devel.kostdoktorn.se/cache-translation-object and gives up to 5x speed increase when using WordPress with “custom” (i.e. non English) localisation files.
MO object created by WordPress is cached and stored in the <code>/wp-content/cache/</code> directory and then used when loading localisations.

l10n cache

Improves site performance by providing caching for localisation objects (*.mo files).

Sergey Biryukov

Converts gettext binary message catalogs to an array of strings. Allows to save some amount of RAM on a shared hosting server. 
Works with plugin and theme textdomains as well as with the default.
Thanks to AlexPTS for the idea.

Pure PHP Localization

Лучший и, скорее всего, единственный рабочий плагин. Спасибо, Сергей

Пожалуй, лучший плагин для кеширования переводов

Converts gettext binary message catalogs to an array of strings.

l10n cache vs Pure PHP Localization